1. Field of the Invention
The invention relates to a cylinder lock and key combination, wherein the lock comprises a cylinder shell, a cylinder key plug rotdrably mounted in the shell, and wherein the key comprises an essentially flat key blade, which is insertable into a key slot in the longitudinal direction of the cylinder key plug and which has a transversally projecting, solid base portion extending in the longitudinal direction and having side recesses for engagement with a row of side tumblers being movably mounted in the cylinder key plug.
2. Description of Background Art
Such a combination is known from SE-B-7906023-2 (GKN Stenman AB), wherein a side shelf at the upper side of the solid base portion of the key blade is substantially perpendicularly oriented relative to the main plane of the key blade. Side recesses extend downwards from the side shelf for engagement with essentially circular-cylindrical side tumbler pins, which in turn engage with a side bar in the region of the shear line between the shell and cylinder key plug of the lock. The side recesses form a coded pattern with code shelf, which define certain mutually engaging positions of the key and the side tumblers, and transitional portions therebetween, said transitional portions being concavely carved in order to enable a movable linear contact with the end edges of the side tumblers when the key is being inserted into the key slot.
The known lock and key system has proven to function very well and has come to wide spread practical use. However, the system is subject to certain drawbacks, viz.:
the key is relatively wide and heavy because of solid base portion, which must have a substantial height (in the plane of the key blade) in order to accommodate a plurality of different levels of the code shelfs, so shelfs, so that the desired number of code combinations can be obtained; PA1 the key slot in the cylinder key plug is by necessity relatively wide in the total height extension corresponding to the solid base portion of the key, which will increase the risk of unauthorized manipulation of the lock by means of picking tools.
Against this background, the object of the present invention is to achieve a lock and key combination which eliminates the above-mentioned drawbacks and which comprises a more slender key and a smaller key slot in the cylinder key plug.
This object is achieved, according to the invention, basically in that the key comprises a lip projecting upwards from the base portion and in that the key slot has a corresponding cross-sectional profile with a downwardly projecting tongue.
As a result of the arrangement with a longitudinal lip, which projects upwards from the solid, wider base portion of the key blade, this solid base potion can be made lower, i.e. having less vertical extension (in the plane of the key blade), since the vertical extension of the lip can also be used for the coded side recesses. Correspondingly, the cross-sectional are of the widened lower part of the key slot will be substantially smaller because of the downwardly projecting tongue, which fits into the space between the lip and the rest of the key blade.
The solid, wider portion of the key blade can be made even lower, if the side tumblers of the lock are non-rotatably guided or rotatable to a limited extent in the cylinder key plug and at least a part of the lower end portion of the respective side tumbler is obliquely curved into conformity with the cylindrical shape of the cylinder key plug.
The side recesses of the key blade may then extend practically all the way down to the lower edge of the key blade, so that the solid, wider base portion of the key blade and the corresponding lower, widened portion of the key slot may obtain a minimal vertical extension.
In case where the side tumblers are non-rotatably guided in the cylinder key plug, the number of code combinations can be further increased in that each side tumbler has an end portion or a side projection, which is specifically longitudinally displaced and which engages with the bottom surface portions of the side recesses of the key, in a corresponding manner as disclosed in the specification U.S. Pat. No. 5,067,335 (Widen). With such a code system, the establishment of a system with master keys and slave keys is facilitated.
Alternatively, the number of code combinations can be increased by making the side tumblers rotatable to a limited extent and positionable in side recesses conformed thereto in the key. The side recesses can then be specifically distributed longitudinally and/or be obliquely positioned.
The invention also relates to a key blank with an upwardly projecting lip, extending at the side along the rest of the key blade. Such a key blank is difficult to manufacture with ordinary locksmith tools. Here, it is an advantage that the manufacture must be made with special equipment in a controlled manner, so that the distribution of key blanks can be controlled and unauthorized production of key blanks is made more difficult.